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4- Pressure:

Everything behaves differently under pressure, especially chemical reactions (like the coffee-making process). As pressure increases, the force on dissolved substances leads to a faster extraction process, which can result in the removal of some substances that do not change in the absence of pressure.

Placing gas under pressure makes it soluble in liquids, resulting in more gas in a pressurized liquid. Releasing the pressure has the opposite effect, causing the gas to be released from the liquid; the most prominent example of this is opening a can of Coca-Cola.

The most famous coffee brewing method using pressure is espresso. Espresso machines produce pressure equivalent to approximately nine times the pressure at sea level. Many dissolved substances appear due to pressure, and water will interact with many gases, resulting in what we call crema.